Pyromellitic diimides of 3,5-dialkyl-4-hydroxyphenylsubstituted amines

ABSTRACT

Pyromellitic diimides of 3,5-dialkyl-4-hydroxyphenylsubstituted amines of this invention effectively stabilize organic materials against the effects of heat and oxygen. The diimides of this invention are prepared by reacting the appropriate 3,5-dialkyl-4hydroxyphenylsubstituted amine with pyromellitic anhydride or pyromelletic diimide. An example of this class of stabilizer is N,N&#39;&#39;-bis(3,5-di-t-butyl-4-hyroxyphenyl)pyromellitic diimide.

United States Patent Dexter et a1.

PYROMELLITIC DIIMIDES OF 3,5-DIALKYL-4-HYDROXYPHENYLSUB- STITUTED AMINES Inventors: Martin Dexter, Briarcliff Manor;

Martin Knell, Ossining; Peter Klemchuk, Yorktown Heights; John F. Stephen, New City, all of NY.

Assignee: Ciba-Geigy Corporation, Ardsley,

Filed: Nov. 13, 1973 Appl. No.: 415,867

Related US. Application Data May 13, 1975 Primary E.\'uminerMelvyn l. Marquis Attorney, Agent, or Firm-Nestor W. Shust [57] ABSTRACT Pyromellitic diimides of 3,5-dialkyl-4hydroxyphenylsubstituted amines of this invention effectively stabi lize organic materials against the effects of heat and oxygen. The diimides of this invention are prepared by reacting the appropriate 3,5-dialkyl-4-hydroxyphenylsubstituted amine with pyromellitic anhydride or pyromelletic diimide. An example of this class of stabilizer is N,N'-bis(3,5-di-t-butyl-4-hyroxyphenyl)pyromellitic diimide.

9 Claims, N0 Drawings DETAILED DESCRlPTlON This invention relates to novel pyromellitic diimide derivatives of 3,5-dialkyl-4-hydroxyphenyl-substituted amines which are useful as stabilizers for organic polymerie materials which are subject to thermal and oxida tive deterioration. The compounds of this invention are represented by the formula:

wherein each of R and R is the same or different (lower) alkyl group of from 1 to 4 carbon atoms; and v has a value of from 0 to 3. Illustrative examples of (lower) alkyl groups of from 1 to 4 carbon atoms which are represented by R and R are methyl, ethyl, propyl, isopropyl, butyl and tbutyl. The preferred groups are methyljisopropyl and t-butyl.

The compounds offormula I wherein y is 0, 2 and3 can be prepared by reacting a 3,5-dialkyl-4-hydroxy phenylsubstituted amine of the formula no (C u -NH wherein R and R is as defined previously, with pyromellitie dianhydride in an inert solvent such as dichlorobenzene at reflux temperatures.

The compounds of formula 1 wherein y is l can be prepared by reacting 3,5-dialkyl-4-hydroxybenzyl dialso kyl amine, of the formula R and R are as defined previously and R is an alkyl group such as methyl or ethyl, with pyromellitic diimide in an inert solvent such as di methyl formamide at approximately 120C.

The 3,5-dialkyl-4-hydroxyphenylsubstituted amines wherein y is 0 can be prepared as described in US. Pat.

The amine, when y is 2 can be prepared for example through chloromethylation of a dialkyl phenol as described in US. Pat. No. 2,838,571, followed by treatment with sodium or potassium cyanide and reduction of the resultant dialkylhydroxyphenyl acetonitrile to the amine. The amine wherein y is 3 can be prepared by reducing 3(3,5-dialkyl-4-hydroxyphenyl)propionitrile with lithium aluminum hydride to yield the corresponding amine. The nitrile can be prepared according to the method described in US. Pat. No. 3,121,732 wherein the appropriate dialkylphenol is reacted with acrylonitrilc. The 3,5-dialkyl-4-hydroxybenzyldialkylamine dialkylamine of formula 111 can be prepared as described by E. P. Previc et al., Industrial and Engineering Chemistry, Vol. 53, No. 6, Page 469,1une 1961.

The compounds of this invention are stabilizers of organic material normally subject to thermal and oxidative deterioration. Materials which are thus stabilized include synthetic organic polymeric substances such as vinyl resins formed from the polymerization ofvinyl halides or from the copolymerization of vinly halides with unsaturated polymerizable compounds, e.g., vinylesters, a,[3-unsaturated ketones, afi-unsaturated aldehydes, and unsaturated hydrocarbons such as butadienes and styrene; polya-olefins such as polyethylene, polypropylene, polybutylene, and the like, including eopolymers of polya-olefins; polyurethanes and polyamides such as polyhexamethylene adipamide and polycaprolactam; polyesters such as polyethylene terephthalates; polycarbonates; polyaeetals; polystyrene; polyethyleneoxide; polyisoprene; polybutadiene and eopolymers such as those of high impact polystyrene containing copolymers of butadiene and styrene and those formed by the copolymerization of acrylonitrile, butadiene and/or styrene.

In general, one or more of the stabilizers of the present invention are employed in amounts, in toto, offrom about 0.005 to about 5 percent by weight of the composition to be stabilized. A particularly advantageous range of the present stabilizers is from about 0.05 percent to about 2 percent. The preferred range is particularly effective in polyolefins such as polypropylene.

These compounds may be incorporated in the polymer substance during the usual processing operations, for example, by milling, or extrusion. The stabilized polymer can be fabricated into films. fibers, filaments, hollow-spheres and the like. The heat stabilizing properties of these compounds advantageously stabilize the polymer against degradation during such processing at the high temperatures generally encountered.

The stabilizers employed in this invention can also be used in combination with other stabilizers or additives. Especially useful co-stabilizers are dilauryl-B-thiodipropionate and distearyl-B-thiodipr0pionate.

The following formula represents co-stabilizers which are in certain instances very useful in combina tion with the stabilizers of this invention:

R-O-C-(C H ll m wherein R is a alkyl group having from 6 to 24 carbon atoms;

and m is an integer from 1 to 6. The above costabilizers are used in the amount of from 0.01 to 2 percent by weight of the organic material, and preferably from 0.1 to 1 percent.

Other antioxidants, antiozonants, thermal stabilizers, ultraviolet light absorbers, coloring materials, dyes, pigments, metal chelating agents, etc., may also be used in the compositions in combination with the stabilizers of the invention.

The following are presented to further illustrate the present invention without introducing any limitation thereto.

EXAMPLE 1 N ,N -bis( 3 ,5-di-t-butyl-4-hydroxyphenyl )pyromellitic diimide The reaction flask was charged with 11.05 grams of 4-amino-2,6-di-t-butylphenol, 5.45 grams of pyromellitic.dianhydride and 100 ml. of o-dichlorobenzene. The reaction mixture was heated to reflux for approximately 2 hours using a Dean Stark trap to remove the water formed. After cooling, the mixture was filtered and washed with petroleum ether. The filter cake was dried and dissolved in 200 ml. of boiling glacial acetic acid and filtered. The product which crystallized on cooling, was filtered, washed with acetic acid, and dried in vacuum over phosphorous pentoxide and potassium hydroxide. The product had a melting point of 304-306C.

Analysis for C H N O t Calculated: C, 73.05; H, 7.10 Found: C, 73.37; H, 7.41

EXAMPLE 2 N,N '-bis[ 2-( 3,5-di-t-butyI-4-hydroxyphenyl)ethyl]- pyromellitic diimide Analysis for C H N- O Calculated: C, 74.09; H, 7.70, N, 4 11; O, 14.10 Found: C, 73.55; H, 7.40; N, 4.12

In a similar manner, by substituting an equivalent amount of 3-(3,5-di-t-butyl-4-hydroxyphenyl)propylamine for 4-amino-2,6-di-t-butylphenol in the above procedure the corresponding N,N'-bis[3-(3,5-di-tbutyl-4-hydroxyphenyl)propyl] pyromellitic diimide is obtained.

EXAMPLE 3 N,N -bis( 3 ,5-di-t-butyl-4-hydroxybenzyl )pyromellitic diimide Analysis for C H N O Calculated: C, 73.59; H, 7.41; N, 4.29; O, 14.71. Found: C, 73.50; H, 7.38; N, 4.28

In a similar manner, by substituting 3-methyl-5-tbutyl-4-hydroxybenzyldimethylamine for 3,5-di-tbutyl-4-hydroxybenzyldimethylamine there is obtained N,N'-bis( 3-methyl-5-t-butyl-4-hydroxybenzyl)pyromellitic diimide with a melting point of 267*269C.

EXAMPLE 4 Unstabilized polypropylene powder (Hercules Profax 6501) was thoroughly blended with 0.20 percent by weight of various compounds of this invention. Also prepared were samples of polypropylene containing 0.1 percent by weight of the stabilizers and 0.3 percent by weight of distearylthiodipropionate (DSTDP). The blended materials were then milled on a two-roll mill at 182C for 10 minutes.

The milled polypropylene sheets were then cut into pieces and pressed for 7 minutes at 218C, on a hydraulic press at 500 psi and then transferred to a cold press at 500 psi. Samples of the resulting 25 mil sheet were tested for resistance to accelerated aging in a forced draft oven at C. The results are set out in Table 1 below:

TABLE I Oven Aging at 150 Additive(s) Hours to Failure distearylthiodipropionate (a synergist for phenolic antioxidants) The above data clearly indicates the significant increase in the stabilization of polypropylene upon addition of the antioxidants of the present invention.

Stabilized polypropylene compositions are also obtained when 0.5 percent of N,N'-bis[3-(3,5-di-t-butyl- 4-hydroxyphenyl)propyl]pyromellitic diimide and N,- N'-bis(3,5-di-t-butyl-4-hydroxyphenyl)pyromellitic diimide respectively are employed alone or in combination with DSTDP.

EXAMPLE 5 To 39.3 g. (0.15 moles) of hexamethylenediammonium adipate were added 0177 g (7.5 X mole; 0.5 mole percent) of hexamethylenediammonium diacetate as molecular weight control agent and 0.183 g (0.5 percent of theoretical nylon yield) of various compounds of this invention. The mixtures were mixed thoroughly and added to Pyrex polymer tubes.

The polymer tubes were evacuated three times and filled with high purity nitrogen each time. The polymer tubes with a continuously maintained, slightly positive nitrogen pressure were placed in a methyl salicylate vapor bath at 222C. The nylon-6,6 salt melted with bubbling due to the liberation of water. After bubbling ceased, a clear'melt was obtained which solidified after 5-8 minutes. After 1 hour at 222C the polymer tubes were transferred to an o-phenylphenol bath at 285C for 1 hour where the solid gradually remelted. The polymer tubes were kept in the 285C vapor bath for an additional one-half hour while they were maintained under oil pump vacuum 1 mm). High Purity nitrogen was then readmitted and the polymer tubes were allowed to cool.

The stabilized nylon-6,6 obtained was ground in a Wiley mill at ambient temperature. About 2 g were heated in a small glass Petri dish in a circulating air, rotary oven at 140C for 65 hours. The viscosities of 1 percent sulfuric acid solutions of aged and unaged polymer samples were determined at C. Stabilizer effectiveness was judged by the percent retention of specific viscosity and by color formation after oven aging. A polyamide containing no stabilizers was prepared and tested in a similar manner and their results with respect to the percent retention of specific viscosity is compared in the following Table 11. The stabilized polyamides had better percent retention of specific viscosity and color retention than the unstabilized polyamide after oven aging.

Table 11 Specific Viscosity Polyamide Percent Retention Unstabilized 65:5 N,N'-bis(3,5-di-t-butyl-4-hydroxy phenyl)pyromellitic diimide 84 NN -bis[ 2-( 3 ,5-di-t-buty1-4-hydroxyphenyl)ethyl1pyromellitic diimide 83 EXAMPLE 6 A quantity of SBR emulsion containing 100 g of rubber (500 ml of cold SBR type 1,500) previously stored under nitrogen, is placed in a beaker and stirred vigorously. The pH of the emulsion is adjusted to 10.5 with a 0.5N NaOH solution.

To the emulsion is added 50 ml of 25 percent NaCl solution. A 6 percent NaCl solution which has been acidified with HCl to a pH 1.5 is added in a thin stream with vigorous stirring. When pH 6.5 is reached, the rubber begins to coagulate and the addition is slowed down in order to maintain uniform agitation. The addition of the acidic 6 percent NaCl solution is terminated when a pH 3.5 is reached. The coagulated crumb-rubber slurry at pH 3.5 is stirred for one-half hour.

The coagulated rubber is isolated by filtration through cheese cloth, and rinsed with distilled water. After three subsequent washings with fresh distilled water, the coagulated rubber is dried, first at 25 mm Hg and finally to constant weight under high vacuum 1 mm.) at 4045C).

The dried rubber (25g) is heated under nitrogen at 125 in a Brabender mixer and to this is added with mixing 0.125 g (0.5 percent) of N,N'-bis[2-(3,5-di-tbutyl-4-hydroxyphenylethyl]pyromellitic diimide. The composition is mixed for 5 minutes after which it is cooled and compression molded at 125C into 5 X 5 X 0.025 inch plaques.

The plaques are placed on .aluminum sheets and heated in a circulating air oven at C for up to 96 hours. The viscosity of a 0.5 percent toluene solution of aged and unaged rubber samples are determined at 25C. Stabilizer effectiveness is judged by the percent retention of specific viscosity, color formation and gel content after oven aging. The stabilized rubber has better viscosity, color retention and less gel content than the rubber which is unstabilized after oven aging.

Similar results are obtained when N,N'-bis(3,5-di-tbutyl-4-hydroxybenzy1)pyromellitic diimide is used in place of the above mentioned stabilizer in the rubber composition.

EXAMPLE 7 A composition comprising linear polyethylene and 0.10 percent by weight of N,N'-bis(3,5-di-t-butyl-4- hydroxyphenyl)pyromellitic diimide retains its physical properties at C longer than one which does not contain the stabilizer.

What is claimed is:

l. A composition of matter stabilized against thermal and oxidative deterioration which comprises an organic polymeric material normally subject to oxidative deterioration containing from 0.005 to 5 percent by weight each of R and R is the same or different lower alkyl group of from 1 to 4 carbon atoms; and

y has a value of from 0 to 3; and from 0 to 2 percent by weight of a co-stabilizer having the formula i l-CH wherein R is :1 alkyl group having from 6m 24 carbon atoms;

and m is an integer from I to 6.

2. A composition of claim 1 wherein said organic polymeric material is polyolefin.

3. A composition of claim 2 wherein said polyolefin is polypropylene.

4. A composition of claim 2 wherein R and R is tertiary butyl or methyl.

5. A composition of claim 4 wherein the co-stabilizer is dilauryl-B-thiodipropionate or distearyl-B-thiodipropionate.

6. A composition of claim 5 wherein the stabilizing compound is N,N-bis(3,5-di-t-butyl-4- hydroxyphenyl)pyromellitic diimide.

7. A composition of claim 5 wherein the stabilizing compound is N,N'-bis[2-(3,5-di-t-butyl-4- hydroxyphenyl)ethyllpyromelli'tic diimide.

8. A composition of claim 5 wherein the stabilizing compound is N,N -bis( 3,5-di-t-butyl-4- hydroxybenzyl)pyromellitic diimide.

9. A composition of claim 5 wherein the stabilizing compound is N,N'-bis( 3-methyl-5-t-butyl-4- hydroxybenzyl)pyromellitic diimide. 

1. A COMPOSITION OF MATTER STABILIZED AGAINST THERMAL AND OXIDATIVE DETERIORATION WHICH COMPRISES AN ORGANIC POLYMERIC MATERIAL NORMALLY SUBJECT TO OXIDATIVE DETERIORATION CONTAINING FROM 0.005 TO 5 PERCENT BY WEIGHT OF A STABILIZING COMPOUND OF THE FORMULA
 2. A composition of claim 1 wherein said organic polymeric material is polyolefin.
 3. A composition of claim 2 wherein said polyolefin is polypropylene.
 4. A composition of claim 2 wherein R1 and R2 is tertiary butyl or methyl.
 5. A composition of claim 4 wherein the co-stabilizer is dilauryl- Beta -thiodipropionate or distearyl- Beta -thiodipropionate.
 6. A composition of claim 5 wherein the stabilizing compound is N,N''-bis(3,5-di-t-butyl-4-hydroxyphenyl)pyromellitic diimide.
 7. A composition of claim 5 wherein the stabilizing compound is N,N''-bis(2-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl)pyromellitic diimide.
 8. A composition of claim 5 wherein the stabilizing compound is N,N''-bis(3,5-di-t-butyl-4-hydroxybenzyl)pyromellitic diimide.
 9. A composition of claim 5 wherein the stabilizing compound is N,N''-bis(3-methyl-5-t-butyl-4-hydroxybenzyl)pyromellitic diimide. 